1. Field of the Invention
The present invention relates to an exhaust-system support device, and specifically to technologies for supporting exhaust-system component parts such as exhaust tubes included in the exhaust system of an automotive engine to conduct exhaust gases from the engine into the atmosphere, and more particularly to a structure of an exhaust-system support fixedly connected to the exhaust-system component part.
2. Description of the Prior Art
The exhaust system of an automotive vehicle is designed to conduct exhaust gases from the engine mounted for instance on the front section of the vehicle body to the rear of the vehicle. The exhaust system, through which exhaust gases leave the engine cylinders, includes the exhaust manifold, exhaust pipe, catalytic converter, sub-muffler, main muffler, tailpipe and/or an intermediate pipe connecting the exhaust pipe to the associated muffler. When mounting such exhaust-system parts on the car frame or floor panel, the exhaust-system parts construct a long assembly extending from the front to rear of the car body, and are hanged on the car frame and/or floor panel by means of a plurality of exhaust mounting bracket or hanger. A typical exhaust-system support device has been disclosed in Japanese Utility-Model Provisional Publication No. 4-109414 or in Japanese Patent Provisional Publication No.4-308314. As disclosed in the Japanese Utility-Model Provisional Publication No. 4-109414 or in Japanese Patent Provisional Publication No. 4-308314, the conventional exhaust-system support device comprises a substantially cylindrical exhaust-pipe clamp with a pair of joinable, two opposing flanged ends through which the clamp is tightly fitted to the exhaust pipe by means of bolts and nuts. The conventional support device also includes an exhaust mounting bracket fixedly connected to the clamp. As is generally known, the exhaust mounting bracket is mounted on the car body (the car frame or floor panel) through an elastic support hanger assembly often called an "exhaust mounting insulator assembly" for the purpose of heat insulation and preventing unusual noises or vibrations to be transmitted to the car body. As set forth above, the prior art exhaust-system support device requires the use of bolts and nuts for tightly fitting an exhaust-pipe clamp onto the outer periphery of the exhaust pipe. This increases the number of parts of the exhaust-system support device, thus increasing manpower in control. In case of the use of bolts and nuts, there is another problem of looseness of bolts and nuts as time goes by. The exhaust system receives forces acting in various directions owing to input vibrations which may be created by the engine and then transmitted to the exhaust system. Even if the bolts and nuts are properly evenly tightened with a specified tightening torque, the bolts and nuts may be loosened each other with the lapse of time. The loosened bolts and nuts result in lowering of supporting rigidity of the substantially cylindrical exhaust-pipe clamp in both the longitudinal and circumferential directions of the exhaust pipe, and thus cause undesired rotation or displacement of the clamped section of the exhaust pipe relative to the exhaust-pipe clamp. As a result, the prior art exhaust-system support device with an exhaust-pipe clamp tightened by means of bolts and nuts, it is difficult to permanently effectively suppress undesired vibrations which may be transmitted to the exhaust system, regardless of the lapse of time. To avoid this, there have been proposed another type exhaust-system support devices as seen in FIGS. 11A and 11B, in which the exhaust-system support device is comprised of an exhaust-pipe mounting hooked portion or exhaust-pipe mounting arm 32 (see FIG. 11A) which is directly welded to the exhaust pipe 30 and adapted to be typically hanged by an elastic support hanger such as a rubber hanger, or an exhaust-pipe hanger bracket 33 (see FIG. 11B) with a hanged pin 34 which is welded to the exhaust pipe 30 and adapted to be hanged by the elastic support hanger. The exhaust-system support device shown in FIG. 11A is formed in such a manner that the hooked portion 32, being formed by way of two-step bending, is directly welded to the outer periphery of the exhaust pipe, whereas the exhaust-system support device shown in FIG. 11B is formed in such a manner that the hanger bracket 33, being comprised of a press-worked metal plate of a substantially C shape in cross section, is welded to the exhaust pipe 30 and then a substantially straight, headed pin 34 is welded to the upper end of the hanger bracket 33. However, in the case that the hooked portion 32 or the hanger bracket 33 is welded to the exhaust pipe 30, the thinner thickness of the exhaust pipe 30 greatly increases the difficulty of welding work of the hooked portion or the hanger bracket to the exhaust pipe. Also, there is a tendency of stress concentration which may be induced in the vicinity of weld bead. Such stress concentration may degrade the durability of the exhaust-system support device.